Large oilfield operations generally employ any of a variety of positive displacement or other fluid delivering pumps. Such pumps may be employed in applications for accessing underground hydrocarbons. These applications may include cementing, water jet cutting, and hydraulic fracturing of underground rock to name a few.
A positive displacement pump may be a fairly massive piece of equipment with associated engine, transmission, crankshaft and other parts, operating at between about 200 Hp and about 4,000 Hp. A large plunger is driven by the crankshaft toward and away from a chamber in the pump to dramatically effect a high or low pressure thereat. This makes it a good choice for high pressure applications. Indeed, where fluid pressure exceeding a few thousand pounds per square inch (PSI) is to be generated, a positive displacement pump is generally employed. Hydraulic fracturing of underground rock, for example, often takes place at pressures of 10,000 to 20,000 PSI or more to direct an oilfield fluid and material through an underground well to release oil and gas from rock pores for extraction.
When employing oilfield pumps, regular pump monitoring and maintenance may be sought to help ensure uptime and increase efficiency of operations. That is, like any other form of industrial equipment a pump is susceptible to natural wear that could affect uptime or efficiency. This may be of considerable significance in the case of pumps for large scale oilfield operations as they are often employed at the production site on a near round the clock basis and may operate under considerably harsh protocols. For example, in the case of hydraulic fracturing applications, a positive displacement pump may be employed at the production site and intended to operate for six to twelve hours per day for more than a week generating extremely high pressures throughout. Thus, wear on pump components during such an operation may present in a variety of forms.
In particular, internal valve seals of the pump are prone to failure, especially where abrasive oilfield material is directed through the pump during a fracturing application as described. These internal valve seals may be of a conformable material in order to allow proper sealing even where the abrasive “proppant” material is present at a sealing interface of the valve. However, the conformable nature of the seal may leave it susceptible to deterioration by this same abrasive oilfield material. Additionally, other components of the pump such as the normally smooth surfaced pumping chamber at the output side of the valves seals may be susceptible to wear by abrasives that are pumped through the pump. Such deterioration of pump components may significantly compromise control over the output of the pump and ultimately even render the pump ineffective.
In order to address pump component deterioration as described, techniques have been developed to monitor acoustics of the pump that present during operation. For example, issues with wearing pump components such as the noted valve seals may be accompanied by certain vibrations particular to the type of wear taking place. Thus, an acoustic sensor may be coupled to the pump to detect high-frequency vibrations particular to a leak or incomplete seal within the chamber of the pump. Such a leak is a common precursor to pump failure. Unfortunately, acoustic detection of leaks or other pump anomalies may only take place once some degree of damage has taken place. That is, acoustic detection of pump problems fails to avoid problem occurrences in a literal sense, but rather only indicates the condition of such problems. Thus, at best there remains the need to take a detected malfunctioning pump out of the operation.
In addition to pump monitoring as described above, efforts have been made to actually prevent pump damage by pumped abrasives. That is, rather than waiting for a minor degree of pump damage to acoustically present as indicated above, efforts have been made to avoid damage to certain pump components altogether. These efforts include introducing abrasives, such as the above described proppant, at locations subsequent to the pressure producing valves and other particularly susceptible oilfield pump components. For example, as detailed in U.S. Pat. No. 3,560,053 to Ortloff, a pressurized abrasive slurry may be introduced to an oilfield fluid after the oilfield fluid has been directed from an oilfield pump. In this manner, the oilfield pump may be spared exposure to the potentially damaging abrasive slurry.
Unfortunately, the above described technique of sparing oilfield pump components exposure to the abrasive slurry is achieved by the addition of a significant amount of equipment at the oilfield. Indeed this added equipment may require its own monitoring and maintenance due to exposure to the abrasive slurry. For example, mixing and blending equipment along with pressurization equipment, including susceptible valving, may be required apart from the primary oilfield pumps described above. Thus, while the original pumps may be spared exposure to abrasives, another set of sophisticated equipment remains exposed, requiring its own degree of monitoring and maintenance.